Radiation of lubricating oils



United S Pflt tQ RADIATION on LUBRICATING ons Alvin M., Natkin, Metuchen, John J. 'Kolfenbach, North Plainfield, and Eric '0. Forster, Scotch Plains, N.J.,

assignors to Essa Research and Engineering Company,

a corporation of Delaware No Drawing. Filed Mar. 1, 1956, Ser. No. 568,710

4Claims. ('Cl. 204158) This invention relates to lubricating oils, and more particularly to a process for improving the physical properties of lubricating oils. In brief compass, the invention pertains to obtaining improved lubricating oils by subjecting the lubricating oils to high intensity ionizing radiation.

In the prior art, when it has been desirable to improve the physical properties of lubricating oils special refining'methods or additives have been employed. For example,'higher viscosity indices of lubricating oils, i.e. the relative degree of change in the viscosity of the oils .20 with respect to temperature changes, have been obtained 3 by means of solvent refining methods or by means of special additives such as polybutene or other high molecular Weight polymers.-

In accordance with the present invention, it has? now been found that lubricating oils having higher viscosity indices as well as other improved characteristics, such as viscosity, color, etc., can be obtained by subjecting the oils to high intensity ionizing radiation. A ln general,

"the'lubrica'ting oils are irradiated with gamma rays.

These gamma rays may be derived from the radioactive decay of certain natural or radioactive elements or isotopes, such as radium 226, radium A, radium B, radium C, radium D, thallium 210, cobalt 60, cesium 137, europium 152-154, cesium 134, cerium 144, silver 1'10, thulium- 170; tantalum 182, scandium; 46, terbium 160, or

iridium 192, or' from chemical compounds of or materials containing such elements or isotopes. The gamma 'raysmay also be derived "from suitably shielded radiation producedin" nuclear reactors, i.e. atomic piles, or

from the spent fuel elements obtained tromthe opera -tion'of such reactors.

' In general, undisturbed gamma ray fluxes within the range ofabout 10 to 6x10 usually about 10 to r f 3x10 ,roentgensper'hour, such; as that derived from a cobalt source, will be employed in irradiating the lubricating oils of'the invention. The time of irradiation will'depend upon the degree of change in the physical propertiesofthe lubricating oils'de'siredas well as upon the radiation'dosage rate.

V Generally, the total, 5 radiation dosage (based on undisturbed radiation field conditions, i.e. conditions prior to the introduction of the lubricating oil into the radiation field) will be within the range of about 10 to 3x10 preferably about 10 to 3x10 roentgens of gamma rays. Thus, irradia- 55 tion time may vary; from about 0.01 to 3000 hours, usually about 0.5 'to'200 hours. For the purposes of this invention, however, thelubricating oil feed stocks may ifbe irradiated tor the shortest period of time required to obtain the desired viscosity indices and viscosities.

V 6 0 i The lubricating oils may also be irradiated in an atomic Patented June 2 7, 1961 ice generally considered to be those neutrons having an energy less than about 30 electron volts (e.g. 0.03 electron volt),- and the slow neutron flux in the atomic pile will be in the range of about 10 to 10 usually about 10 to 10 neutrons/cmfi/sec. T-he gamma ray flux will generally be about 10 to 6x10 usually about 10 to 3x10 roentgens per hour. The radiation of an atomic pile will also contain a certain amount of fast neutrons having an undisturbed flux of about 10 to 10 usually about 10 to 10 neutrons/cmfi/sec.

Any of the known mineral or synthetic lubricating oil base stocks may be employed as the feed material in the invention. In general, these lubricating oils should have a viscosity of about 10 to 2,000, preferably about 20 to 1,000 centistokes at F. and about 1 to 100, preferably about 2 to 50 centistokes at 210 R, an A.S.T.M. pour point of about +40 to -7S F., a flash point of about 300 to 650 F., and a viscosity index of about 0 to 175, preferably about 20 to 160. Mineral lubricating oil base stocksderived, from paraflinic, naphthenic and mixed. base crudes having the properties listed above are especially useful in preparing the improved lubricatingoils of-the invention. As hereinafter shown,-however, the phenol-treated naphthenic base lubricating oils are particularly preferred in that theyshow. the most improvement in physical properties with little or no deleterious efiects when subjected to irradiation.

The synthetic lubricating oils which may also be employedinclude esters of monobasic acids (e.g. an ester of C Oxo alcohol with C Oxo acid, an ester of C Oxo alcohol with octanoic acid, etc.), esters of dibasic acids (e.g. di-2-ethy1 hexyl sebacate, di-nonyl adipate, etc.), esters of glycols (e.g. C Oxo acid diesterof tetraethylene glycol, etc.), complex esters (e. g. the complex ester formed by reacting one mol of tetraethylene glycol with two moles of sebacic acid and two moles of 2-ethyl-hexanol, or the complex ester formed by reacting one mole of tetraethylene glycol, one mole of adipic acid, one mole of C Oxo alcohol-and one mole of C Oxo acid, etc.), esters of phosphoric acid (e.g.. the ester formed by contacting three moles of the mono-methyl ether of ethylene glycol with one mol of phosphorous oxychloride, etc.), halocarbon oils (e.g. the polymer of chlorotrifluoroethylene containing twelve recurring units of chlorotrifluoroethylene) carbon- .ates (e.g. the carbonate formed by reacting C 0x0 alcohol with ethyl carbonate to form a half ester and reacting this half ester with tetraethylene glycol), m'ercaptals (e.g.

' the mercaptal formed by reacting Z-ethyl hexyl mercaptan with formaldehyde), formals (e.g. the formal formed by'i'eacting C 0x0 alcohol with formaldehyde), polyglycol type synthetic oils (e.g. the compounds formed by condensing butyl alcohol with fourteen units of propylene oxide, etc.), or mixtures of the above in any proportions.

-.The irradiation of the lubricating oil feed stock may be carried out by a variety of procedures. For example,

the radioactive source may be placed in a tank containing a suitable lubricating oil to carry out-a batch operationor the radioactive source may be placed into a stream of such lubricating oil to carry out a, continuous process. The lubricating oil .may also be piped through an atomic reactor or pile as a continuous stream wherein the oil is exposed to the neutrons and gamma rays.

Many obvious modifications of these procedures be 3 apparent to those skilled in the art. The utilization of radiation emitted by radioactive materials necessitates, of course, the provision of adequate radiation shielding means and techniques. Sue-h means and techniques are, however, well known in the art and need not be described herein in detail.

The irradiation of the lubricating oils may generally be carried out at temperatures within the range of about 20 to 400 F. or higher. Ordinarily, the irradiation will be carried out at a"'temperatur e of about 50 to atmospheres.

However, one of the advantages of the 'presentprocess is that" it maybe effectively utilized at room temperatures and atatmospheric pressure. "If car- 15 set forth in the "table below:

- higher boiling polymeric material or lower boiling'hydro- (5) Lubricating Oil B-A phenol-treated naphthenic type oil having a viscosity of 20.5 cs. at 100 F. and 3.7 cs. at 210 F., 54.3 V.I., an API gravity of 289, a flash point of about 340 F. and a pour point of about -50 F. This lubricating oil was derived from a Coastal crude.

(6) Lubricating Oil FA parafiinic type oil having a viscosity of 86.0 cs. at 100 F. and 10.0 cs. at 210 F., 104.8 V.I., an API gravity of 30.2, a flash point of about 485 F. and a pour point of about +20 F. This lubricating oil was derived from a Mid-Continent crude.

(7) Lubricating Oil GA synthetic oil comprising C Oxo formal having a viscosity of 16.0 cs. at 100 F. and 3.60 cs.at-210 F. I

The-inspections of the irradiated lubricating oils are Table 1 EFFECT DEV-RADIATION N LUBRICATING OILS Viscosity, Gentlstokes V.I. Neut. No. Change In Oolor Lubigcgting at 100 F. at 210 F.

i p i Before After Percent Before After Before After Before After 'Percent Before After Percent Increase Increase Increase 198.8 250.2 25.8 12.5 14.4 15.2 36.1 36.3 0.5 0.04 0.08 Reddlsh --Reddish f brow-n. yellow. 857.0 1,165.0 26.4 "39.6 49.2 24.2 87.5 90.2 3.1 0:19 0.19 Greenlsh- Greenlsh I -black., black. 12.7 21.4 68.6 3.4 4.8 42.3 156.1 159.0 1.8 '0. 12 9.21 Colorless" Colorless.

268.3 344.0 28.4 "14.9 17.5 17.5 34.2 "38.6 12.8 0:03 0.02 Greenish -Gree'nlsh M a brown. yellow. 20.5 25.5 25.1 "3.7 4.3 14.8 54.3 61.0 12.5 0. 06 0.02 Yellow Straw 1' M v :2 bl-own.- yellow. 86. 0 112. 30. 8 10. 0 12. 3 22. 3 104. 8 107. 2 2. 3 0. 06 0. 12 Yellgw Yellow. "re "16.14 20.40 27.0 346) 4.23 17.0 4213.3 129.3 7.6 0.03 30.53

bonaceous solids or hydrocarbon materials having boiling points outside of the lubricating oil boiling-range,"e.g.

- caibons;are formed the irradiated lubricatingoil may be ,recoyeredby any'of the conventional methods; e.g. filtration, distillation, etc.

p The following examples and tables are presented to illustrate the preparation and the various characteristics of '-the improved lubricating oils of the-invention.

EXAMPLE I 'The undisturbed radiation" intensityof this sourcewas "abont212 roentgens7hour. The following lubricat- .ingoil'samples'we're exposed to radiation of'thisintnsity for 168' hours:

(I) Lubricating 'Oil'A-An acid-treated naphthenic Thislubricating oil was derived from a' coa'stal "crude.

(2) Lubricating Oil"B Aparatfinic"type' oil having a. viscosity of 857 cs. at 100 F. and 39.6 cs. at 210 F.",87.5"" fV.I.," an API gravity of 22.0", aflash 'poinfof 560" F. and a pour point'of-FZS" F. This lubricating 'oil"was "derived from a Mid-Continent crude residuum.

di-2-ethylhexyl'sebacate'having a viscosity 'of 12.7 cs: at

4) Lubricating Oil D -'-A-"phenol treated naphtlienic Theabove data showthat the high intensity igamma ray irradiation of lubricatingoils will result in marked changes in the physical-properties of the lubricating oils. The data further show that paraflinic type mineral-lubricating oils are less susceptible to change in certain properties by irradiation than the naphthenic typemineral lubricating oils, particularly the phenol-treated naphthenic'oils, while the synthetic type lubricating-oils :are the most affected. It should be noted, however, that the synthetic lubricating oils, as represented by- Lubricating Oil C, show a-very large increase in their'neutralization number in contrast to the mineral lubricating oils which do'not show anychange at all in this respect.

The lubricating oils produced in accordance" with the present invention may be employed in lubricating oil compositions and in lubricating grease compositions. Furthermore, the lubricating oils of the present invention may haveminor proportions of conventional lubricant: additives incorporated therein. More'particularly; the lubricating oils may contain detergents (e.g. barium nonyl phenol sulfide, calcium 'sulfonates), oxidation inhibitors (e.g phenyl alpha-naphthylarnine; di-tertiary I butyl-paracresol), corrosion inhibitors (e.g. zinc dihexyldithiophosphate), rust inhibitors, dyes, anti-foaming agents, etc.

The lubricating grease compositions maycontain conventional grease thickeners such as fatty acid soaps (e.g.= calcium stearate) soap-salt or mixed salt complexthickeners (e.g. calcium acetate-calcium stearate), polyethylene, polybutene, silica gel, carbon black, etc. aswell as -the conventional inhibitors listed above.

5 In accordance with one aspect of this invention. how- 'ever, it is importantnot to have the conventional additives present during irradiation. As shownin the following' example, the presence 'of conventional oiridationinhibitors during irradiation will result ina loss of their "effectiveness as antioxidants and,-'in some instances, will minimize i the chan'ges in the physical 1 ptoperties 'f'ofigthe EXAMPLE II The following lubricating oils and the lubricating oil compositions were irradiated in a manner similar to that of Example I except that field intensity was 1.74

roentgens per hour: 5

Table 11 Micro Viscosity, Alcoa Os. Neut. Oxida- Lubricant N 0. tion 10 Life, 100 F. 210 F. Hrs.

Lubricating Oil F- Before 86. 65 9. 987 0. 01 30 After 111. 60 11. 94 0. 01 28 15 Lubricant Composition R: 3

Before" 86. 03 9. 90 0. 05 90 After 98. 09 10. 89 0. 01 27 Lubricant Composition 8:

Before 86. 29 9. 92 0.05 360 112. 80 12. 07 0. 02

1 Time to 60 mm. Hg pressure drop.

2 Lubricating 011 F plus 0.8 wt. percent Oxidation Inhibitor A and 0.05 wt. percent Rust Inhibitor A.

3 Lubricating 011 F plus 0.4 wt. percent Oxidation Inhibitor B and 0.05 wt. percent Rust Inhibitor A 4 A phenol-treated naphthenic SUS at 210 F.

6 Lubricating Oil H plus 0.4 wt. percent Oxidation Inhibitor A and 0.075 Wt. percent Rust Inhibitor B.

6 An acid-treated naphthenic lubricating oil having a viscosity of i0 SUS at 210 F. plus 0.4 wt. percent Oxidation Inhibitor B, 0.2 wt. percent Oxidation Inhibitor A and 0.05 wt. percent Rust Inhibitor A.

It will be further understood that the invention is not necessarily limited to the specific materials and operating conditions of the foregoing examples. These materials and conditions may be varied within the limits indicated in the general portions of the specification.

What is claimed is:

1. A method of increasing the viscosity and viscosity lubricating oil having a viscosity of 66 index of a lubricating oil which comprises exposing a lubricating oil having initially a viscosity in the range of 10 to 2000 cs. at 100 F., a pour point in the range of to F., and a flash point in the range of 300 to 650 F., to gamma irradiation until in the range of 10 to 3 x10 Roentgens of energy have been absorbed, and recovering a lubricating oil product having an increased viscosity and viscosity index.

2. The method of claim 1 wherein the gamma dosage is in the range of 10 to 3X10 Roentgens per hour.

3. A method of increasing the viscosity and viscosity index of a naphthenic lubricating oil which comprises exposing a naphthenic base lubricating oil having initially a viscosity in the range of 10 to 20.00 cs. at F., a pour point in the range of +40 to 75* F., and a flash point in the range of 300 to 650 F., to gamma irradiation at a temperature in the range of -20 to 400 F. until in the range of 10 to 3 10 Roentgens of energy have been absorbed, and recovering a lubricating oil product having an increased viscosity and viscosity index.

4. A method comprising exposing a phenol treated naphthenic type oil having initially a viscosity of 14.9 cs. at 210 F., a viscosity index of 34.2, and an API gravity of 222, a flash point of about 440 F and a pour point of about 0 F., to gamma irradiation obtained from cobalt 60 at a dosage of about 2.2 l0 Roentgens per hour for 168 hours, and recovering an improved product having a viscosity of 17.5 cs. at 210 F. and a viscosity index of 38.6.

Relative Merits of Cathode Rays and Gamma Radiations, by Goldblith and Proctor, from Nucleonics, February 1954, vol. 12, No. 2, pp. 32-35.

Radiation Stability of Plastics and Elastomers, by Bopp 40 & Sisman, from Nucieonics, vol. 13, No. 7, July 1955, pp. 

1. A METHOD OF INCREASING THE VISCOSITY AND VISCOSITY INDEX OF A LUBRICATING OIL WHICH COMPRISES EXPOSING A LUBRICATING OIL HAVING INITIALLY A VISCOSITY IN THE RANGE OF 10 TO 2000 CS. AT 100*F., A POUR POINT IN THE RANGE OF +40* TO -75*F., AND A FLASH POINT IN THE RANGE OF 300* TO 650*F., TO GAMMA IRRADIATION UNTIL IN THE RANGE OF 10**6 TO 3X10**9 ROENTGENS OF ENERGY HAVE BEEN ABSORBED, AND RECOVERING A LUBRICATING OIL PRODUCT HAVING AN INCREASED VISCOSITY AND VISCOSITY INDEX. 